1. Field of the Invention
This invention relates to a long-lived activator additive for the life extension of the lead-acid batteries and a battery using the additive.
2. Description of Related Art
Conventionally, the inventors and others discovered that polyvinyl alcohol and polyacrylic acid had an effect to increase the hydrogen overvoltage of the electrode in diluted sulfuric acid and were effective in eliminating the sulfation of deteriorated battery and in making a new battery long-lived, and applied for patents (For instance, see patent document 1, patent document 2, and patent document 3).
However, polyvinyl alcohol, added to the acid electrolyte, has a considerable foam formation (hydrogen gas production at the negative electrode) when the charge current is large, the sulfuric acid is carried out from the upper hole of the battery. This over flow of the acid sometimes corrodes the battery terminal metals and the battery container case. Another problem of the polyvinyl alcohol is the short effective life period: the polymer is oxidized at the positive electrode slowly and the molecule is decomposed and the concentration is reduced. Therefore for the good effect, the polymer must be added once a year or every other year.
The polyacrylic acid or its alkali metal salt is very effective, but the viscosity of the solution is very high, a good solution was difficult to produce. Also the powder is difficult to dissolve to the battery acid electrolyte. For the dissolution of the polyacrylic acid, agitation for long time is required.